This invention relates to apparatus for cleaning the submerged portion of ship hulls, specifically for removing barnacles and marine growth from ship hulls, especially painted metal hulls without damage to the hull.
It is well known that any object immersed in the ocean attracts various forms of marine organisms which settle and grow on its surface. This significantly affects ships in maritime commerce, which are significantly affected by hull form degradation form the growth of such organisms. The most deleterious such organisms are barnacles, hard shelled marine organisms which form an irregular, high drag growth upon the surface of the hull, significantly reducing the efficiency of ship operation and increasing the cost of such operation. Barnacles form a strong calcerous bond to any submerged object, and grow hard calcium based shell structures, which are extremely resistant to abrasion. Removal of such growth without damage to the ship hull is a difficult task.
In large ocean going vessels, for example tankers, the economics of vessel operation are such that it is prohibitively expensive to periodically dry dock the ship for cleaning and scraping; nonetheless marine growth must be periodically removed from the hull so as to prevent nonacceptable degradation in ship performance. For this reason there has been a long felt need for an apparatus which is capable of removing marine organisms and barnacle growth from a hull while the ship is in the water. Further, such an apparatus must effectively smooth the hull without removing protective paint and without damaging the hull.
The prior art apparatus for this purpose is complicated by the underwater environment. Since there is generally no surface against which such a unit can be braced or push for positioning or stability, the nature of the cleaning forces is limited to such forces as will not push the apparatus away from the hull. For this reason, the prior art has developed various forms of counterrotating brushes or rotating abraders, which do not produce significant net reactive forces in use, and thus do not push themselves away form the work.